Ultrastructural localization of adrenergic nerve terminals in the circular muscle layer and muscularis mucosae of the rat duodenum after acute treatment with 6-hydroxydopamine.

The ultrastructure of the intrinsic adrenergic innervation of the circular muscle coat and muscularis mucosae of rat duodenum has been studied following acute treatment with 6-hydroxydopamine. Adrenergic terminals were found among intramuscular nerve bundles. They were most numerous in the outer layer of the circular coat, where close neuromuscular contacts were commonly encountered. Adrenergic terminals also innervated the inner layer of the circular coat and the muscularis mucosae, where only wide neuromuscular contacts have been found. The evidence suggests that smooth muscle cells in the rat duodenum may be directly influenced by adrenergic nerves.